Spring steel fins for up-hole sensor installation

[TeejT]

Hi All,

I'm working on an addition to a mining sensor which will enable it to be installed into up-holes (i.e. holes in the ceiling) and "grapple" it in place. Without going into too much irrelevant installation detail, I built a quick prototype with four fins cut from .025" thick aluminum sheet (see photo).

The sensor is the steel cylinder. As it's pushed into the hole, the fins bend back and prevent the sensor falling back out as intended. The prototype worked very well in proof of concept testing and I have some other modifications in mind including doubling the number of fins and adding a centralizing structure, but anyway the relevant question I have is as follows:
The aluminum sheet is obviously not the right material for this. It doesn't spring back after deformation and isn't very resilient to abuse/mishandling. I think I need some sort of sheet spring steel instead.
Any informed suggestions on the material to go with would be highly appreciated! Thanks a lot!

 

[btrueblood]

I'd think about using a mechanism like that in rock climbing cams.

 

[TeejT]

Neat idea, but it needs to be very inexpensive, simple, and, like I said, this concept worked very well for the strength required (sensor is cemented in place once it reaches desired position). Just needing advice to help narrow in on the type of steel with less trial and error.

 

[Compositepro]

Spring steel strips like yours can be purchased from many vendors.

http://www.mcmaster.com/#standard-spring-steel-sheets/=12oifdg

 

[drawoh]

TeejT,

You are designing springs. You need a material with a high yield stress in relation to its elastic modulus. That material is not aluminium. You have cantilever beams that must bend some minimum distance without yielding. Probably, you have more deflection than double integration will reliably analyze, so you will have to check your mechanics of materials textbooks. Spring steel is (not surprisingly) a good spring material. Beryllium copper and titanium are better spring materials, if not exactly cheap and/or RoHS compliant. A lot of plastics might work.

--
JHG

 

[TeejT]

Thanks guys. I'm going to go with 1095 spring steel sheet, .025" for starters and see how that goes. Any other suggestions please shoot.

 

[Tmoose]

Would the grapple rely solely on friction?
Does the grapple need to "dig into" the pipe?
Does the sensor need to be centered in the pipe?

The exhaust pipes in an auto parts store are often stored by installing secure but removable hooks like these -

http://www.amazon.com/Walker-Exhaust-35729-Hardware-Pipe-Hook/dp/B001AX85QC

 

[dvd]

Try high carbon steel banding - there are other sources than McM-Carr... It is cheap. Stop by a lumberyard or warehouse and beg a piece for trial.

http://www.mcmaster.com/#strapping-components/=12p5ksy

 

[tbuelna]

A couple questions for you.

1) Will the magnetic properties of the spring material affect the sensor performance? Obviously the non-magnetic aluminum spring material worked OK. But will a magnetic material like carbon steel also work?

2) Is corrosion resistance over the service life of the sensor housing a concern? If so, you might want to use a stainless steel material for the spring, or apply some type of coating.

3) Since cost is a concern, rather than using a bolt to attach the spring as shown in your photo above, you might consider making the spring from a material that would allow it to be welded to the sensor housing.

Good luck with your project.

 

[zeusfaber]

If the hole diameter is reasonably well controlled, another approach might be a coil spring (bit like something out of a spring mattress)- twist and push to insert, twist and pull to retrieve, but secure for as long as you aren't twisting.

A.